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Hot water tank temperature

The majority of households in the UK rely on water tanks for central heating and hot water. However, not many people are aware of how a hot water tank works or how to spot potential problems until the damage is done. We will explain key points to be aware of for anyone who owns a hot water tank or is thinking about getting one.

What is a hot water tank?

A hot water tank, also known as a hot water cylinder, is heated by a boiler or immersion Hot water is then stored in the hot water tank for when it’s needed. Cold water storage tanks may be needed for central heating and hot water.

How does a hot water tank work?

Hot water is stored in the hot water tank ready for use. There are two types of tanks, Vented & Un-vented.

A “vented” hot water tank is heated by a coil of pipe inside which is connected to the boiler. There may be an immersion heater which sits in the side of the tank which is fed by a cold water storage tank (usually in the loft or airing cupboard).

An “un-vented” hot water tank is also heated by a coil of pipe inside which is connected to the boiler, again there may be an immersion heater which sits in the side of the tank. The water in the tank is fed directly from the cold water mains. It doesn’t require a cold water storage tank.

In both cases, the water in the tank is heated by the hot water traveling from the boiler. It is pumped through a copper coil inside the water tank, this coil heats the water inside the tank which is then used at the taps/showers etc.

What temperature should my hot water tank be set at?

A hot water tank temperature in the UK should be between 60°C to 65°C.

If the temperature is below 50°C, there’s an increased risk of growing bacteria such as Legionella that causes Legionnaires disease. This happens when your water has been stagnant in the water tank for a while.

If the temperature is above 65°C, then the water will be too hot to use and it increases the risk of serious burns. Keeping the temperature at a safe level, 60°C to 65°C, makes the water hot enough to use and hot enough to kill unwanted bacteria.

To be on the safe side, hot water tanks are now required by law to be fitted with a thermostat to allow the temperature of the water in the tank to be set. Some hot water temperature sensors will allow you to keep track of the water tank temperature on your phone.

Are hot water tanks energy efficient?

The average household’s water tank usage is 14% to 18% of its energy consumption. Making them possibly a high-cost item. This is why it’s great to seek alternative methods to save energy while using the hot water tank.

The good news is that modern water tanks are 100% energy efficient because they recycle the energy used from heating the water. This gives them the reputation of being great at retaining a set temperature. Gas boilers are 80% to 90% energy efficient and tend to reduce over time. Gas boilers lose their heat through the vent system or roof.

Another way to save on energy is by setting the best temperature on the thermostat. This maintains the tank's temperature efficiently. It could also help you save on energy costs, for example storing at 60°C rather than 65°C. However, always beware of Legionella risk if the thermostat is set below 50°C.